Positive engagement latch for a pushbutton actuator with local and remote release



Nov. 26, 1968 w. G. DENNISON POSITIVE ENGAGEMENT LATCH FOR A PUSHBUTTON ACTUATOR WITH LOCAL AND REMOTE RELEASE 2 Sheets-Sheet 1 Filed Oct. 13, 1966 Nov. 26, 1968 w. G. DENNISON 3,413,578 POSITIVE ENGAGEMENT LATCH FOR A PUSHBUTTON ACTUATOR WITH LOCAL AND REMOTE RELEASE Filed Oct' 13, 1966 2 Sheets-Sheet 2 United States Patent 3,413,578 POSITIVE ENGAGEMENT LATCH FOR A PUSH- BUTTON ACTUATOR WITH LOCAL AND RE- MOTE RELEASE William G. Dennison, Milwaukee, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Filed Oct. 13, 1966, Ser. No. 586,519 Claims. (Cl. 335167) ABSTRACT OF THE DISCLOSURE A positive engagement latch for the depressible shaft of a pushbutton actuator for a switch. A pair of springbiased pivotal levers snap into an annular groove in the shaft when the pushbutton is depressed to lock it. Manual release by turning the pushbutton causes a cross pin in the shaft to separate the levers from the groove. Electrical release by a magnet attracting a concentric armature causes the levers to be pivoted out of the groove to release the shaft for restoring under spring force. The latch is housed within the retaining ring of a one-hole mounting pushbutton.

This invention relates to pushbutton latches and more particularly to mechanical latches for locking pushbutton shafts or the like combined with remote release by electrical means and/or local release by manual means.

While not limited thereto, the invention is especially applicable to latching the axially movable actuator or operating member of a pushbutton switch.

An object of the invention is to provide an improved latching mechanism adapted for latching a depressible operating member such as a pushbutton shaft or the like.

A more specific object of the invention is to provide an improved latching mechanism combined with remote electrical release means or local manual release means.

Another specific object of the invention is to provide an improved latching mechanism combined with both remote electrical release means and local manual release means.

Another specific object of the invention is to provide an improved electrically and manually releasable latch for the depressible actuator of a pushbutton switch.

Another specific object of the invention is to provide an improved latching mechanism which minimizes the effects of sliding friction which could otherwise cause considerable variance in the performance of the device throughout its life span.

Another specific object of the invention is to provide an improved latching mechanism incorporating subassemblies which simplifies the complete assembling operation.

Other objects and advantages of the invention will hereinafter appear.

These and other objects and advantages of the invention and the manner of obtaining them will best be understood by reference to the following description of an exemplary embodiment of a pushbutton latch taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a top plan view of a pushbutton incorporating a latch constructed in accordance with the invention;

FIG. 2 is a cross-sectional view taken along line 22 of FIG. 1 showing the pushbutton switch actuator in its normal or unlatched position;

FIG. 3 is a cross-sectional view like FIG. 2 but showing the pushbutton switch actuator in its operative or depressed and latched position;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 showing a bottom view of the latching mechanism;

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FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 3 showing the latching mechanism in its manual release position; and

FIG. 6 is an exploded view partly broken away of the latching mechanism.

Referring to FIG. 2, there is shown a portion of a mounting plate 2 having a round hole in which a pushbutton incorporating a latch according to the invention is mounted. This pushbutton which is adapted to be used as an actuator for an electric switch is of the oiltight type, that is, it is sealed against the entry of oil from the pushbutton side of the mounting panel either into the pushbutton mechanism or through the hole to the other side of the mounting plate.

As shown in FIGS. 1 and 2, the pushbutton is provided with means for mounting it onto the mounting panel and for housing the internal parts. This means comprises a generally tubular retaining ring 4 which has an external flange 4a at the lower end, an internal wall 4b at its midportion and external threads 40 from a point near the flange to a point near the internal wall. This retaining ring is also provided with one or more drain holes 4d, angularly spaced degrees if more than one, immediately above the internal wall to drain out any oil or other liquid that may enter the upper portion when the pushbutton is horizontally mounted in either of two positions turned 90 degrees.

To assemble the pushbutton to a mounting panel, an annular gasket 6 is placed on flange 4a, the upper portion of the pushbutton is inserted through the hole in the panel and a generally tubular retaining nut 8 is screwed onto threads 40 on the other side of the panel to clamp the panel between the nut and the flange with the gasket therebetween.

.Internal wall 4b is provided with means for guiding and registering a switch actuator such as shaft 10a of a pushbutton assembly 10. This means comprises a round vertical hole extending through an upper boss at the middle of the internal wall and through the wall and through cam portion 4e intergral with this internal wall and extending downwardly therefrom around the center hole. The pushbutton assembly comprises an insulating pushbutton 10b mounted rigidly by a set screw to a die cast button cast on the upper end of the shaft and a spring pin 10d extending through a hole in the intermediate portion of the shaft for manually releasing the latch as hereinafter described. The pushbutton assembly further includes a combined stop and contact actuator such as a washer 10e removably secured by a flat head screw to the lower end of the shaft for depressing the switch operators or plungers partially shown in dotted lines when the pushbutton is pressed. This washer is removable to permit substitution of different voltage rating magnets.

Means is provided for normally holding the pushbutton in its upper position and for returning the pushbutton thereto after it has been depressed. This means comprises in the illustrated embodiment an helical spring 12 bearing at its upper end against the lower peripheral portion of the pushbutton and stopped at its lower end on internal wall 4b. This pushbutton return spring also comprises a part of sealing means. For this purpose, a generally conical sealing member or diaphragm 14 has a hole at its smaller upper end, the rim of which is retained in an annular groove in shaft 10a just below button 10c and grips the reduced portion of the shaft in such annular groove to form a seal impervious to liquid such as oil. The lower larger end of diaphragm 14 has an external annular flange 14a which rests on an annular rib formed on the upper surface of internal wall 4b. An annular ring 16 of metal rests on annular flange 14a and spring 12 presses down on ring 16 whereby the flange and diaphragm 14 is pinched between the ring and the rib to form a seal and to prevent any liquid from entering the space around the shaft.

The space below internal wall 4b is provided with means for automatically latching the pushbutton assembly in its depressed position and affording either manual or electrical release. This means comprises a pivot plate 18 on which are pivoted a pair of latch levers 20 and 22. These latch levers are biased by springs 21 and 23, respectievly, to engage an annular groove 10 in the shaft to latch the pushbutton assembly in its lower position in response to depression thereof.

The means affording local manual release of the latch comprises the aforementioned spring pin 10d having its opposite ends extending in opposite directions from the shaft and a pair of shoulders on each latch lever adjacent the end portions of the pin whereby rotation of the pushbutton in either direction pivots the latch levers outwardly to release the shaft for return upwardly.

The means affording remote electrical release of the latch comprises an electromagnet for pivoting the latch levers outwardly to release the shaft. This electromagnet comprises a coil 24 wound on an insulating bobbin 26 and mounted in an electro-magnetic frame assembly comprising a magnet body 28 and a magnet cap 30. This coil, bobbin, magnet body and magnet cap as sembly is rigidly held together by being enclosed in encapsulating compound such as epoxy 32 with a pair of terminals 34 partially embedded in the molded epoxy and being electrically connected to the coil by conductors extending through holes in the frame and bobbin and adapted for connection to a remote external circuit. This electromagnet also includes a hollow armature 36 slidably received above the washer and magnet on the lower end portion of shaft 10a within the coil and an insulating insert 38 made of nylon or the like which is snap secured and glued to the armature and which engages the free ends of latch levers 20 and 22 to effect an electrical release of the latch when the coil is energized.

The shapes of the various parts are shown more clearly in the isometric view in FIG. 6. As shown therein, cam portions 4e are formed in the downwardly extending tubular portion of internal wall 4b by downwardly diverging cutout portions in the front and rear sides thereof. These cutout portions continue as slots 4f in the sides of the center hole in internal wall 4b and the boss thereon. As will be apparent, these cam portions provide upwardly converging walls to cam spring pin 10d and the shaft back into their normal, unrotated position when the return spring moves the pushbutton assembly up.

Internal wall 4b is also provided with means for registering and rigidly securing pivot plate 18 thereon. This means comprises a pair of short downwardly extending cylindrical projections 4g which enter corresponding holes 18a and are flattened thereover to keep the pivot plate from turning relative to retaining ring 4 and to secure it thereon.

Plate 18 is provided with means for pivotally supporting the two latch levers thereon. This means comprises a central cutout portion of generally rectangular shape terminating at its rearward and forward ends in downwardly bent portions or tabs 18b, each having a, pair of spaced pivot pin holes therein. As will be apparent, the rectangular cutout portion of plate 18 provides space for cam portions 4e to extend downwardly therethrough. And latch levers 20 and 22 are pivotally supported by pivot pins in the holes in downwardly bent portions 18b as hereinafter described.

As shown in FIG. 6, latch levers 20 and 22 are alike but are turned in opposite directions to face one another. Latch lever 20 will be described in detail since latch lever 22 is similar thereto. As shown at the left-hand portion' of FIG. 6, latch lever 20 is provided with a generally.

horizontal flat body portion 20a having rear and front arms 20b bent upwardly and extending toward the right. These arms have holes at their ends matching the lefthand holes in downwardly bent portions 18b of the pivot plate and are secured thereto by pivot pins as shown in FIG. 4.

The latch levers are provided with combined bias spring retaining means and shock proofing means. These means comprise a first shoulder pin 200 secured at the upper left portion of body portion 20a by being riveted in a hole in the latter. As shown in FIGS. 2 and 3, this shoulder pin serves as a retainer for the lower end of an helical compression spring 21, the upper end of this bias spring being anchored in a downward projection 18c extruded from pivot plate 18. A pair of similar shoulder pins 20d is secured to the lower midportion surface of body portion 20a by being riveted to holes therein. All three of these shoulder pins are preferably formed of metal such as copper or the like having a predetermined heavy weight to enhance the resistance of the latch to shock. That is, these shoulder pins form weights on the latch levers to counterbalance the weight of the armature assembly to shock as much as possible and thereby tend to prevent release of the latch.

As shown in FIG. 6, each latch lever is provided with an arm whereby electrical release is accomplished. For this purpose, latch lever 20 is provided with an arm 20e bent downwardly from the rear right-hand portion of body portion 20a and then bent back toward the right so that it extends behind shaft 10a and then curves forwardly in the same plane into the lateral plane of the shaft so that its end portion is centered relative to the shaft. In a similar manner, the corresponding arm of latch lever 22 passes down and then to the left in front of shaft 10a and then curves rearwardly to be centered to the left of the shaft as shown in FIGS. 3 and 4.

As shown in FIGS. 2, 3 and 6, armature 36 is hollow and has a cylindrical upper portion 36a open at the top and a frusto-conical lower portion 36b terminating at its lower end in a hole through which shaft 10a extends. To form a magnetic air gap of constant width, magnet body 28 is generally cup-shaped to enclose the coil and its bottom portion has a center hole for shaft 10a surrounded by an upstanding portion extending part way upwardly within the coil and having a frusto-conical depression complementary to the lower end of the armature to form an air gap. The upper cylindrical portion of the hollow armature has an annular internal groove 360 which is first filled with adhesive and into which snap the four legs 38a of insert 38 when the insert is pressed into the armature. For this purpose, each such leg has a tooth on its outer side which enters the groove in the armature and the adhesive therein to rigidly hold the two parts together.

The upper portion of insert 38 is provided with means for engaging the long arms Ne and 22e of the latch levers. For this purpose, insert 38 is provided with left and right extending portions 38b, each curved upwardly at its end and having an aperture therein for receiving the corresponding arm of the latch lever. As shown in FIG. 2, the latch lever arm engaging portions of insert 38 are rounded so that they will slide freely on the latch lever arms as the armature moves down.

Spring pin 10d is preferably made from a flat strip of spring metal rolled along its long axis to a slightly larger diameter than the hole, squeezed at one end and inserted into the hole in shaft 10a and frictionally held therein by its natural tendency to restore to its former diameter.

It will be apparent from the foregoing description that this pushbutton latch is especially adapted for actuating an electrical switch. In actual practice, a pair of screws are used to secure the magnet assembly to the flange of the retaining ring. These screws extend through holes in encapsulating epoxy member 32 and are threaded into tapped holes 4h (FIG. 1) in the flange of the retaining ring. Modular switches may be secured to the magnet assembly, one below the other, in a similar manner except that each pair of screws threads into tapped holes in the heads of the previous pair of screws to hold the parts in stacked relation.

When the pushbutton is depressed from the position shown in FIG. 2 to that shown in FIG. 3, return spring 12 is compressed and the shaft moves Washer 102 down to actuate switch plungers 42 thereby to open or close contacts as desired. When the pushbutton is depressed far enough so that groove f in the shaft reaches arcuate abutting portions 201 and 22) of the latch levers, springs 21 and 23 suddenly rotate latch levers and 22 counterclockwise and clockwise, respectively, and snap these arcuate portions against the reduced portion of the shaft within the groove. This same action causes arms 20e and 22e of the latch levers to raise insert 38 and armature 36 so that there now is an air gap between the armature and the magnet as shown in FIG. 3. In this position, arm 20e is free of downwardly bent portion 22g of latch lever 22 and arm 22e is free of a similar downwardly bent portion 20g on latch lever 20. This position is now stable since latch lever 20 is confined between its pivot and shaft 10a under bias of springs 21, 12 and the return springs of the switch contacts. Latch lever 22 is similarly confined between its pivot and shaft 10a under the bias of its springs 23, 12 and the return springs of the switch contacts.

For local manual release of the latch, it is only necessary to rotate the pushbutton in either direction a small amount. This causes spring pin 10d to engage the shoulders on arms 20:: and as shown in FIG. 5 and to rotate the latch levers outwardly out of the groove in the shaft thereby to release the shaft whereupon return spring 12 snaps the pushbutton assembly back into its upper position. If the pushbutton is rotated in one direction, spring pin 10d pushes on the shoulders on arms 20:: and 22e to release the latch. If the pushbutton is rotated in the other direction, the spring pin pushes on downwardly bent portions 20g and 22g with the same result. Under extreme rotation shoulder pin 20c will stop against projection 18c to prevent spring pin 10d from snapping behind any of the shoulders on these arms and catching therein.

Electrical release is accomplished from a remote location by energizing the coil. This causes the magnet to attract the armature. Consequently, insert 38 pulls down on arms 20e and 22e to pivot the latch levers outwardly thereby to release the latch.

When the latch is released manually and the return spring snaps the pushbutton assembly upwardly, spring pin 10d engages the flared edges of cam portion 4e. This causes the pushbutton assembly to be cammed into realinement or centered so that it can be depressed again and so that spring pin 10d will not stop against body portions 20a and 22a of the latch levers.

The structure hereinbefore described is especially adapted for use as a pushbutton latch because it can be made small enough to fit inside the lower portion of the round sleeve or flanged retaining ring of a pushbutton with its release magnet occupying a space equal to the space otherwise occupied by one switch contact block. For example, this latch will fit inside the lower portion of a retaining ring having an internal diameter of substantially one inch. This small size of latch capable of latching a return force of many pounds is brought about by the general arrangement and structure of the parts. It will be noted that annular groove 10 in the shaft is provided with a beveled or chamfered lower side. This bevel reduces the frictional force counteracting opening of the latch. Also, on electrical release as soon as arcuate portions 20 and 22 of the latch levers have left the horizontal lower wall of groove 10 this bevel cams them outwardly to relieve the load on the electrical release magnet. This structure allows mere pulsing of the magnet coil with electrical current to be used to release the latch or allows continuous energization of the magnet without noise or overheating. This structure also affords use of a much smaller alternating current magnet without the use of shading coils. Since the load is completely removed from the magnet upon release of the latch, continuous energization of the magnet would provide momentary action for the pushbutton, that is, the pushbutton restores as soon as it is released if the magnet is held energized. Also, shaft 10a will have no tendency to creep under vibration when the latch is engaged. Moreover, since the latch mechanism is entirely positioned below internal wall 4b, the space above this wall is left free to facilitate sealing the device and making it impervious to liquid or the like.

As most clearly seen in FIGS. 2 and 3, the pushbutton latch may be assembled by first making subassemblies to facilitate final assembling thereof. The pushbutton assembly is made by casting metal button onto the knurled, enlarged end of the shaft, securing the plastic pushbutton 10b by a set screw onto the die cast button, inserting spring 12 and bearing washer 16 on the shaft and then inserting diaphragm 14 in the annular groove adjacent the button whereby its flange holds spring 12 against the pushbutton. Spring pin 10d is then forced into the hole in the shaft and this assembly is then inserted into retaining ring 8. Washer like is left off for now. It will be noted that slot 4 is cut all the way through internal wall 4b and through the boss on the latter to allow assembling of the spring pin on the shaft beforehand which is much easier.

The latch subassembly is then put together and secured below the internal dividing wall. For this purpose, insert 38 is secured to the armature, the arms of the latch levers are placed in the apertures in insert 38 and the latch levers are pivotally secured to pivot plate 18 by two pairs of rivets or pivot pins. This subassembly is then inserted in retaining ring 8 so that projections 4g on the lower surface of the internal wall extend through corresponding holes 18a in the pivot plate and these projections are flattened or riveted over the edges of these holes rigidly to secure the pivot plate in place.

The magnet assembly is then made by winding the coil on the bobbin, placing this in the magnetic frame, placing the magnetic cap over the coil and molding all of it into a body of epoxy. This magnet assembly may then be secured to the lower flange of the retaining ring by a pair of screws. The assembly may then be completed by securing washer 102 by a flat, round head screw to the lower end of the shaft. After that, one or more switch contact blocks may be secured to the magnet assembly therebelow. For an illustration and description of suitable switch con-tact blocks for this purpose, reference may be had to W. F. Nolden and C. F. Robbins Patent No. 2,930,859, dated Mar. 29, 1960, Class 200-16. Finally the pushbutton end of the assembly may be inserted through a hole in a mounting panel and securing collar or retaining nut 8 threaded on the retaining ring -to rigidly mount the pushbutton switch to the panel.

From the foregoing, it will be apparent that the struc-:

ture disclosed is constructed and arranged to provide an improved pushbutton latch and also to facilitate assembly thereof by way of subassemblies.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that I do not intend to confine my invention to the particular preferred embodiment of pushbutton latches described, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

I claim:

1. In an actuator having a guiding portion and an actuator member movably supported in said guiding portion including spring means for biasing said actuator member to a normal position and being depressible therefrom to an operating position, an automatic latching mechanism for latching the actuator member in its operating position comprising:

tion of the actuator member for moving said latch levers away therefrom thereby to release and allow return of the actuator member to its normal position.

2. The invention defined in claim 1, wherein said local manual release means comprises:

shoulders on said latch levers adjacent to and on opposite sides of the actuator member;

and lateral projections on the actuator member for engaging said shoulders when the actuator member is rotated to pivot said latch levers away therefrom and effect said release.

3. The invention defined in claim 2, together with:

cam surfaces on the guiding portion converging in the return direction of said actuator member for camming said lateral projections to rotate said actuator member back concurrently with return thereof to its normal undepressed position.

4. The invention defined in claim 1, together with:

electromagnetic release means adapted for operation from a remote location for moving said latch levers away from the actuator member to release the latter and comprising: an electromagnet including an armature movable relative thereto;

arms on said latch levers extending past opposite sides of the actuator member with each arm extending below the other latch lever;

and means on said armature effective when operated by said electromagnet for pulling on said arms to pivot said latch levers away from the actuator member to release the same.

5. The invention defined in claim 4, wherein said catch means comprises:

narrow flat shoulders on the actuator member engaged by said portions of the latch levers to latch the actuator member in its operating position;

and bevels next to said narrow flat shoulders for camming the latch levers in opposite pivotal directions as soon as the actuator member is released and starts to return under the force of its spring means thereby to remove the load from the electromagnet.

6. The invention defined in claim 5, wherein said narrow flat shoulders and bevels are provided by:

a partially beveled annular groove around the actuator member which is a round shaft.

7. In a pushbutton switch having a tubular housing adapted to be mounted in a hole in a panel and including an internal dividing wall having a hole forming a guide for slidably accommodating the shaft of a switch actuator assembly having a pushbutton on the outer end of the shaft and a compression spring above the internal wall for biasing the pushbutton for returning the assembly to its normal position after the pushbutton has been depressed into its operating position, the improvement comprising:

latching means for latching the switch actuator assembly in its operating position comprising:

two similar latch levers arranged on opposite sides of the shaft and each including a shaft engaging portion and an operating arm bent at two places to form a shoulder therein with the free ends of these arms extending past the shaft behind and in front thereof, respectively;

means pivotally suspending said latch levers from respective pivot points close to the axis of the shaft;

a groove in said shaft for receiving said shaft engaging portions of the latch levers;

means resiliently biasing said latch levers against the shaft so that said shaft engaging portions enter said groove when the pushbutton is depressed to latch the switch actuator assembly in its operating position;

and tripping means for rotating said latch levers against said biasing means out of said groove to release said shaft for return to its normal position.

8. The invention defined in claim 7, wherein said groove in said shaft comprises:

a short fiat inner shoulder against which said shaft engaging portions of the latch levers abut to latch the shaft;

and the remainder of the corresponding side of said groove outside of said flat shoulder being chamfered to the outside of the shaft to form a cam surface for further separating said latch levers after they are released from said flat inner shoulder.

9. The invention defined in claim 8, wherein said means pivotally supporting said latch levers comprises:

means providing a pair of pivot points for each latch lever in a common plane with that portion of said flat inner shoulder which forms a catch for the shaft engaging portion of the respective latch lever and said common plane being parallel to the axis of the shaft whereby the load on said shaft is substantially completely removed from said tripping means leaving only the friction between said shaft engaging portions and said fiat inner shoulder to be overcome thereby.

10. The invention defined in claim 7, together with:

an electromagnet assembly around the inner end portion of said shaft rigidly secured to said tubular housing and adapted for receiving one or more switch contact blocks in stacked relation thereon;

an armature slidable on said shaft and arranged for attraction by said electromagnet assembly;

means coupling said armature to the operating arms of said latch levers for pivoting the latter to release said shaft when the electromagnet is energized;

and a fiat member removably secured to the inner end of the shaft serving as a stop against said electromagnet assembly for the return movement of said shaft and adapted to actuate the switch contacts when the pushbutton is depressed.

References Cited UNITED STATES PATENTS 1,052,595 2/1913 Lanphier 335174 3,209,102 9/1965 Boley 335-171 3,213,237 10/1965 Mikina 335167 3,217,125 11/1965 Brackett 335-167 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner. 

